1. Field of the Invention
The invention relates to a light emitting apparatus and a method for manufacturing the same.
2. Background Art
In the field of light emitting apparatuses for lighting appliances and the like, improvements in recent years of the performance of solid state light emitting devices such as LEDs (Light Emitting Diodes) and LDs (Laser Diodes) have enabled rapid progress to replace incandescent lightbulbs and fluorescent lamps with solid state light emitting apparatuses. Reasons driving such progress for solid state light emitting devices include long life, the lack of toxic substances, and great energy conservation benefits for lighting appliances, which account for several ten % of the total energy consumption.
Conventionally, when applying solid state light emitting devices to lighting appliances and the like, a solid state light emitting device package including, for example, a solid state light emitting device chip combined with a fluorescer to emit white light is mounted on a printed circuit board with an IC forming control/drive circuits and the like and electronic components such as resistors, diodes, condensers, etc.
In such a case, the heat produced by the solid state light emitting device causes the luminous efficacy of the chip to decrease and the life of the chip and the electronic components, etc., recited above to shorten. Such problems are extremely serious for practical use, and technology has been discussed to use, for example, a substrate having a structure of at least two layers of an isotropic thermally conductive layer and an anisotropic thermally conductive layer to efficiently dissipate heat from an LED (for example, refer to JP-A 2007-123348 (Kokai)).
Further, the conventional art of individually constructing each of the IC forming control/drive circuits and the like and the electronic components such as resistors, diodes, condensers, etc., and then disposing the same on a printed circuit board is time-consuming and costly. Moreover, in the case where many solid state light emitting devices are arranged to form an illumination apparatus having a large surface area, many more electronic components are necessary to monitor and control the intensity of the emitted light of each of the solid state light emitting devices to obtain uniform illumination; the interconnects for such electronic components become complex; and problems during manufacturing are even more serious.
On the other hand, display apparatuses using, for example, liquid crystals, organic electroluminescence (EL), and the like use substrates on which thin film transistors (TFTs) and interconnects are formed for pixel driving. Providing solid state light emitting devices on such substrates is expected to eliminate manufacturing problems because the interconnects and the various electronic devices for driving the solid state light emitting devices can be formed collectively on the substrate in any configuration. However, glass substrates normally used in display apparatuses and the like have low thermal conductivities; and it is difficult to dissipate heat efficiently from the solid state light emitting device. Moreover, glass substrates are transparent and undesirably reduce the efficiency as a light emitting apparatus because the light emitted by the solid state light emitting device also is emitted from the bottom side of the substrate.